Thermal Energy Harvesting to Power a Battery-Less Node of a Wireless Sensor Network

A commercial Peltier cell is experimentally characterized working as a thermoelectric generator for small temperature differences between 1°C and $4^{\circ}\mathbf{C}$. The method proposed, consisting of simple experiments together with the model used, can be applied to characterize other thermoelectric generators for similar applications. The measurement results of the output voltage of the Peltier cell for a given resistive load, aid the designer of the energy harvesting circuit to fulfill the specifications of the particular application. A system is implemented to show the feasibility of having a small wearable Peltier cell as the only source of power for a wireless sensor node. The node is IEEE 802.15.4 compliant and transmits three messages every $10 \mathbf{min}$. In order to adapt the voltage level provided by the Peltier cell to supply the node, an energy harvesting circuit is built based on an off-the-shelf DC-DC converter.